Rotor blade coning angle

[automan1223]

I am curious about when making a hub bar for a rotor system.

What is the importance of coning angle that is built into the bar. ?

What if you had too much or too little ?

What is the range of degrees that were tried or are acceptable with non powered rotor systems. ?

Also is it better to have the angle bent into the bar at the teeter block or is it better to have the coning angle formed at the outer ends of the bar.



Thanks
Jonathan

[gyropilot]

Jonathan,

Having the approximate coning angle built into the hub simply reduces bending stresses which would otherwise occur in the blades, blade straps, and the hub bar. The rotor blade system is going to have to find a place to cone one way or the other, so building the bend into the hub bar allows you to control where it happens.

Likewise, if you have too much or to little coning angle built into the hub bar, then the residual coning angle will have to occur someplace else... like bending the hub bar, at the blade straps, or somewhere along the blades themselves. There's no acceptable range of degrees for the coning angle per se... you either have it correct or you don't and any error is simply absorbed somewhere in the rotor system. It's something that can be calculated with reasonable accuracy.

If and where you build in the coning angle in is at the discretion of the rotor system designer and should be based on sound engineering principles. Rotor Flight Dynamics (Dragon Wing blades) bend the coning angle into the hub bar (apparently in a press) just outside of the rotor head's teeter stops. Rotordyne hub bars have the coning angle machined into the ends of a very thick straight hub bar. In this later case the hub bar has to be thick (and consequently heavy) to accommodate the machined ends. The Bensen, Brock and Rotor Hawk hub bars I've seen have no coning angle at all built in.

See the attached graphic from Chuck Beaty to understand more about coning angles and undersling.

Best regards,

John L.

[automan1223]

Thanks so much John,

That sheds some light on my question. I have to get that magical book called Chuck Beaty. A gyro encylopedia on legs.

Jonathan

[jucie]

Great, John.

Does anyone knows where that "2900" in the formula came from?

I know we have very knoledgeable people here too, like Doug Riley (a smart guy that never minds to share a little with us), but I simply cann't accept as a fact of life that we lose access to all that unvaluable archives at Norm's forum. What to say about the insightfull people that didn't come here?

Chuck Beaty, where are you??? I know you don't even read e-mail, as you explained to us some time ago, but please show up, guy. I know you don't have to, but be nice with yours fans, come on!